There are many different types of electrodes, ranging from essentially non-consumed electrodes such as those found in batteries and electro-hydrolysis, to consumable electrodes found in electroplating and electro-remediation. There are also many different methods of producing electrodes. Perhaps the simplest method is providing an electrode as a solid mass of metal or alloy. Solid copper, platinum, silver, lithium and zinc electrodes, for example, are all widely employed. Other methods involve sputter coating or other application of a conducting material onto a substrate.
Negative battery plates in lead-acid batteries typically fall into the substrate coated type of electrodes. Such electrodes are generally prepared by placing a lead oxide paste onto a lead grid, where the lead serves as both an electrical conductor and a mechanical frame for the paste. The lead in the frame is normally alloyed with a small proportion of a second metal, such as antimony, in order to stiffen the grid and allow it to be subjected to normal processing. After the lead grids have been pasted with lead oxide paste, opposed plates are disposed in a sulfuric acid bath and subjected to a charging cycle, whereby positive and negative plates are formed. In the case of the negative plates, the lead oxide paste is converted to sponge lead, and the plates are then ready for incorporation into a battery.
The heavy metallic grid can also be eliminated in a negative battery plate by substituting a grid composed of a light weight, non-conductive material that has an initial minimal degree of conductivity imparted thereto. The grid is then pasted with the desired metal oxide, and converted to the elemental metal by electrolysis. The conversion of the oxide to metal by electrolysis may be initiated by a single conductive lug in contact with the battery paste at one corner of the grid, a plastic grid may be provided with a thin coating of metal by electrode position, or a separate conducting element may be pressed into contact with the battery paste during charging and then removed when charging has been completed. Although the conductivity of the plate is initially fairly low, the electrolytic metal initially formed progressively increases the conductivity of the plate and sustains and accelerates the oxide to metal conversion.
Each of these processes, which can be generically referred to as conversion of "green "batteries, generally involves high costs, including expenditures of relatively large amounts of energy. It is also common for heating and other degradation of the sulphuric acid or other electrolyte to occur, requiring the electrolyte to be replaced several times during a single conversion process. At least some of these problems are related to increased internal resistance developed during the conversion process.
Thus, there is a continuing need to improve electrode manufacturing processes, and in particular to improve curing of electrodes during green battery conversion.